Electron dynamic beam convergence apparatus for color receiver



R. R. E'DEL 3,187,218 ELECTRON DYNAMIC BEAM CONVERGENGE 'APPARATUS FORCOLOR RECEIVER June 1, 1965 2 Sheets-Sheet 1 Filed July 5, 1962 2Sheets-Sheet 2 R. R. E'DEL June l, 1965 ELEcTEoN DYNAMIC BEAMcoNvERGENcE APPARATUS EOE coLoR RECEIVER Filed July 5, 1962 ldfilPatented .lime l, i965 ice This invention relates to color image displaysystems and particularly to means for making a plurality of electronbeams of a multiple beam display device converge at all scanned pointson the target electrode of said device.

An illustrative example or" such a multiple beam display device is acolor liinescope. Color kinescopes of the shadow mask type normally havethree electron guns positioned in the neck of the liinescope and atarget electrode includinn an apertured shadow mask located bctween theelectron guns and a luminescent screen of phosphor dots. The dots arearranged in groups of three in register with respective apertures of themasl. Means are provided for the three electron beams converge at thecenter of the scanned area of the target electrode. The three beams,after passing through the shadow mask, respectively strike threephosphor dots, each emitting light of a different color. All three beamsare eilected by a common horizontal and vertical deflection system sothat the beams systematically scan the kinescope target'. The more thethree beams are deflected from the center or the target, unlesscorrective measures are taken, the greater may be the misconvergence ofthe beams when they reach the shadow mask. It is, therefore, customaryto provide dynamic electromagnetic rneans for correcting themisconvergence of the beams as a function of the angular deflection ofthe beams from the center of the kinescope target. For this purpose,current waveforms of generally parabolic shape are derived from thehorizontal and vertical deflection cir cuits and are employed, inconjunction with three convergence eleclromagnets, to dynamicallyconverge the three beams at all points or the entire scanned area of thelrinescope target.

The waveforms employed must have proper shapes in order to achieve goodconvergence of the three beams at all points of the kinescope target.The waveform requirements may be estimated by observing the unconvergedrasters of the three beams. It has been observed that color picture tubesystems operating with relatively large angles of deilection, as forexample 9i), require more correction at the outer edges of the scanned.area when the undeflected beams are statically converged at the centerof the picture area. Because of this requirement, the dynamic waveformmust have greater amplitude and precision in order to elect satisfactoryconvergence throughout the scanned picture area. Not only are thewave-shaping requirements more severe in more recent systems havinggreater .angles of beam deliection, but also considerably moredetiecting force is needed to suitably effect the desired beamconvergence.

Therefore, it is an object of the invention to provide an improved highemciency circuit by which to edect convergence of the three electronbeams of a tri-color kinescope..

The present invention is embodied in a beam convergence circuit such asthat disclosed in Patent No. 2,963,- 622, granted September 8, 1959, tel. Schopp. in such apparatus the convergence electromagnet circuitsappear essentially inductive to voltage pulses impresse' thereon fromthe horizontal deflection circuits. Hence,

these pulses are effectively integrated to form generally sawtooth waveswhich are impressed upon coils incorporated in the circuits tor excitingthe convergence electro- CII magnets. A second integration of thesesawtooth waves is effected by the convergence control circuits toproduce the substantially parabolic current waves desired for traversalof the electromagnet windings. Circuits such as those disclosed in theSchopp patent include a resistivecapacitive circuit which functions toadd a sawtooth component to the current traversin(7 each of theconvergence electromagnet windings. Such a component is used because theparabolic current waves produced in the manner described do not alwayshave the proper shape to achieve the desired beam convergence.

The present invention is embodied in such a circuit and one feature ofit comprises the connection of a unilateral conducting device (eg. adiode) across the resistive element of the circuit by which the sawtoothwave component is produced. The connection of this unilateral conductingdevice is such that it is gated on (Le. rendered conductive) during thelatter part of each beam trace period. Such operation decreases thelosses in the beam convergence circuits suitably to 'improve the waveshape of the current traversing the electromagnet winding and thereby toeffect better beam convergence. During the rst part of each beam traceperiod, the unilateral conducting device is substantially non-conductingso that the resistive element across which it is connected may beadjusted to provide an optimum discharge rate for the capacitive elementin the savvtooth wave-forming circuit, thereby improving the beamconvergence during the rst part of each beam trace period.

The Schupp patent also discloses the series connection of a diode and aresistor in parallel with each beam convergence clectromagnet forproperly proportioning the alternating current (A.C.) and direct current(D.C.) components of the current Waves traversing the convergenceelectromagnets. Another feature of the present invcntion, which may beused separately or in conjunction with other features, is a parallelarrangement of a diode and a resistor connected in series with theconvergence electromagnet. By such an arrangement, less power is used toeilect the desired beam convergence without detracting from theperformance of the circuit. Thus, rela-` tively high er'lciency ofoperation is achieved.

For a better understanding of the invention together With additionalobjects, features and advantages thereof, reference will be made to theaccompanying drawings in which:

FIGURE 1 is a block diagram of a color television receiver in which thepresent invention is embodied;

EEG/URE 2 is a fragmentary sectional view of the neck portion of ashadow mask color kinescope showing the relationship of the convergenceelectromagnets and the electron beams respectively controlled thereby;

FIGURE 3 is a circuit diagram, partly in block form and partly inschematic form, of the beam convergence circuits embodying a unilateralconducting device in the sawtooth Wave-developing circuit by which waveshaping is improved;

FIGURE 4 comprises a series of curves for use in describing theoperation of the wave-shaping feature of the invention;

FIGURE 5 is a schematic circuit diagram of the corivergence circuit forone electromagnet showing the waveshaping unilateral conducting devicein conjunction with the parallel connection to the clectromagnet of aseries diode and resistor arrangement for A.C.to-D.C. componentproportioning as disclosed in the Schopp patent; and

FIGURE 6 is a schematic circuit diagram of the convergence circuit forone electromagnet showing the waveshaping diode feature of the inventionin conjunction with the additional feature of a parallel arrangement ofa diode anar/,sie

and resistor for A.C.to-D.C. component proportioning connected in serieswith the convergence electromagnet.

Reference Vfirst is made to FIGURE l for a general description of acolor television receiver embodying the present invention. Radiatedsignals received by the antenna 11 are processed in the TV receivercircuits 12 in a known manner to produce video signals representingthree component colors of image to be reproduced and synchronizingsignals for controlling beam deflection and for other purposes such asthe production of suitable signals by which to effect convergence of thethree electron beams at the target electrode of the image-reproducingcolor kinescope. The receiver circuits 12 may be of the type disclosedin Color Television Service Data, 1961, No. T6, furnished by RCA SalesCorporation, Indianapolis, Indiana.

The color television receiver also includes a three beam color kinescope13 serving as a color image-reproducing device such as a shadow maskcolor kinescope of the RSA type Z-IFBPZ'Z or ZlFJPLZlZ. The red, greenaud blue representative signals received from the receiver Vcircuits 12are impressed respectively upon electron guns 14, 15 and 16 of thetri-color kinescope 13. The three electron beams produced by these gunsare deflected together over the target screen o-f the kinescope underthe control of a deflection yoke 17. Also the beams are maintained linconvergence with each other by means of a suit-ably energized beamconvergence yoke 1S, an illustrative form of which will be descibedsubsequently.

Also derived from the receiver circuits 12 are horizontal and verticalsynchronizing signals which are impressed upon a synchronizing signalseparator 19. The horizontal synchronizing signals are impressed uponthe horizontal deflection circuit 21 and the vertical synchronizingsignals are impressed upon the vertical deflection circuit 22. Thehorizontal and vertical deflection circuits are connected to thedeflection yoke 17 as indicated by the reference characters H--H andV-V. All of the apparatus of FIGURE 1 described up to this point may beof the same character as that disclosed in the service data previouslyreferred to.

Signals derived from the horizontal deflection circuit 21 at thehorizontal deflection rate are impressed upon horizontal convergencecircuits 23, the output of which is connected to the convergenceelectromagnets of the convergence yoke 18. Details of suchconvergencecircuits by which suitable convergence waves are producedwill be described subsequently. Signals at the yvertical deflection ratederived from the vertical deflection circuit 22 are impressed upon thevertical convergence circuits 24 for the production of suitable waveswhich also are impressed upon the electromagnets of the convergence yoke18. The vertical convergence circuits are not part of the presentinvention and may be of a known type such as disclosed in the Schopppatent.

Reference now is made to FIGURE 2 for a description of thephysicalrelationship of the convergence electromagnets and the electron beamscontrolled respectively thereby as presently embodied in commercialcolor television receivers. This figure is a transverse sectional viewof the neck portion of a color kinescope as it appears when viewed fromthe luminescent screen end of the kinescope. The three electron beams 25pass respectively between pairs of pole pieces 26, 27 and 28 locatedinternally of the neck 29 of the kinescope 13. These pole pieces extendinwardly from the ends of substantially U- shaped cores of green, redand blue vconvergence electromagnets 31, 32 and 33 respectively mountedexternally around the neck of the kinescope. Each of the convergenceelectromagnets is provided with a horizontal deflection frequencywinding and with a vertical deflection frequency winding. The horizontaldeflection frequency windings are designated 34S, 34R and 34Brespectively for the green, red and blue electromagnets 31, 32 and 33.The vertical deflection frequency windings are designated 35G,

K and 35B respectively for the green, red and blue electromagnets 31, 32and 33. Energization of the electromagnetl windings produces a magneticfield between the corresponding pole pieces which moves thecorresponding electron beam radially. There also may be included as partof the convergence electromagnetic structure some means for effecting astatic convergence Of the electron beams 25. The static convergencemeans may be permanent magnets associated with the respectiveconvergence electromagnets or may comprise windings on the respectiveelectromagnets for energization by direct current of the properamplitude and polarity to effect the desired static convergence of theelectron beams. Such static convergence means is known and, since itforms no part of the present invention and is not needed for anunderstanding of this invention, it is not shown.

FIGURE 3 illustrates generally the connections of the horizontalconvergence circuits 23 and the vertical convergence circuits 24 betweenthe horizontal and vertical deflection circuits 21 and 22 respectivelyand the windings of the green, red and blue convergence electromagnets31, 32 and 33 respectively. The horizontal deflection circuit 21includes a deflection output tube 36 and an output transformer 37. Thiscircuit is connected in a known manner to the horizontal deflection yokeand to the high voltage rectifier circuits as indicated. The outputtransformer also is provided with a secondary winding 38 in whichvoltage pulses at the horizontal deflection repetition rate areproduced. These pulsesY are impressed upon the green, red and bluehorizontal convergence circuits 39, 41 and 42. Each of theseconvcergence circuits converts the voltage pulses derived from thetransformer winding 38 into suitably shaped parabolic current waves fortraversal of the associated horizontal deflection frequencyelectromagnet windings 34G, 34R and 34B.

Also, voltage pulses at the vertical deflection repetition rate derivedfrom the vertical deflection circuit 22 are converted bythe green, redand blue vertical convergence circuits 43, 44 and 45 respectively intosuitably shaped parabolic current waves for traversal of the associatedvertical deflection frequency electromagnet windings 35G, 35K and 35Brespectively.

The present invention relates principally to the horizontal convergencecircuits of which the blue horizontal convergence circuit 42 isrepresentative. Hence, only this circuit'will be described in detail.The voltage pulses derived from the secondary winding 38 of thehorizontal deflection output transformer 37 are impressed uponlaparabola amplitude control coil 46, the inductance of which may bevaried as indicated by means such as a ferrite core movable within thecoil in a known manner. The coil 46 is connected to one terminaliof thewinding 34B of the blue convergence electromagnet'SS, the other terminalof this winding being grounded. Connected in parallel across the winding34B is a series arrangement of a capacitor 47 and a potentiometer 48connected as a variable resistor, The blue horizontal frequencyconvergence electromagnet circuit appears essentially inductive to thevoltage pulses developed in the transformer winding 3S principally byreason of the inclusion of the amplitudecontrolling coil 46. Hence,these pulses are effectively integrated to cause a generally sawtoothcurrent wave to traverse the coil 46. A second integration of thissawtooth wave is effected by the convergence control circuit(principally the essentially inductive winding 34B) toproduce thedesired substantially parabolic current wave for traversal oftheelectromagnet winding 34B. ln order yto shape Vthe parabolic wave tobetter effect the desired convergence, a sawtooth current wave componentis cornbined with the parabolic wave. This additional sawtooth currentfor tilting or phasing the parabolic current traversingthe electromagnetwinding 34B is produced by the series arrangement of the capacitor 4'7and the variable resistor 48. The amplitudeof this sawtooth wavecomponent and hence the amount of tilting of the parabolic Wave isdetermined `'oy the adjustment of the variable resistor 48.

It has been found that the shape of the parabolic current Wavetraversing the electromagnet Winding 34B for example, is not in allcases entirely adequate for eliecting Ibeam convergence in color picturetube systems operating with relatively large angles of beam deflection.The wave shaping is materially improved by connecting a unilateralconducting device such as a diode 49 in parallel across the variableresistor i8 in the polarity indicated. In prior art circuits, which didnot include the diode 49, the best adjustment of the resistor 48 was acompromise between a value which would provide an adequate dischargerate for the capacitor 47 to eiect satisfactory shaping of thesubstantially parabolic current Wave during the initial portion of atrace period and which would suitably reduce circuit losses in thelatter portion of a trace period to effect satisfactory Wave shapingduring such latter portion.

In operation or" the blue horizontal convergence circuit d2 of FIGURE 3,the diode i9 is substantially non-conducting during the iirst portion ofeach horizontal beam trace over the target electrode of the colorkines/cope. The variable resistor may be adjusted to an optimum valuefor eiiecting discharge of the capacitor d? during the initial traceperiod which produces a material improvement in the shape of theparabolic current Wave traversing the electromagnet Winding 3dB duringsuch period. The diode i9 is cond .cting during the latter portion ofeach horizontal beam trace period, thereby decreasing the losses in thecircuit. The resultant shape of the parabolic current Wave through theelectromagnet winding 34B is thereby improved so that better convergenceofthe color lzinescope electron beams is achieved, particularly in thosesystems using color lcinescopes operating with relatively widedeflection angles.

The improved shape of the parabolic current Wave is illustrated by thecurves of FIGURE 4. The solid line curve 5l represents the voltagedeveloped across the convergence electromagnet such as the Winding 3dBof the blue electromagnet 33 in prior art circuits such as thatdescribed in the Schopp patent. This curve 5l is substantially linearthroughout the entire beam trace period. As a consequence, the solidline curve 52 represents the shape of the current traversing theelectromagnet winding during the beam trace period. Although the shapeof this curve 52 is substantially parabolic, it has a relatively sharp.peak portion 53 at the middle of the horizon-tal beam trace and sideswhich do not have suihcient ste-epilees to effect entirely satisfactorybeam convergence at the beginning and ending of the beam trace,especially in color kinescopes having relatively wide deilection angles.

The inclusion of the Wave-shaping diode rfi-9 of EEG- URE 3 in the bluehorizontal convergence circuit d2 alters the shape of the voltage Waveacross the convergence electromagnet Winding as represented by thebroken line curve of FiGURE 4. This curve is no longer linear duringbeam trace intervals, but instead decreases more rapidly during thefirst part of trace and again more rapidly during the final part oftrace. During the central portion of beam trace the voltage curvechanges at a slower rate than in the first and unal parts or trace. As aresult, the substantially parabolic current Wave which traverses theelectromagnet winding has a shape substantially as illustrated by thebroken curve line 55. This curve has somewhat steeper sides at both thebeginning and ending of beam trace than in the previous case. Thissteepening results from the greater slope of the voltage Wave 54.-during these portions of the beam trace interval. Also, the curve 55 hasa ilatter peak portion during the middle of beam trace which resultsfrom the lesser slope of the voltage Wave 541 during this period. Theenergization of the convergence electromagnet windings by substantiallyparabolic current Waves having the shape f the curve 5S has been foundto produce significantly better dynamic beam convergence over the entirescreen of a color kinescope operating with relatively Wide deflectionangles.

The novel features of the convergence circuit described with referenceto FIGURE 3 also may be used in convergence circuits such as those`disclosed in the Schopp Patent 2,903,622 previously rete red to. FlGURE5 illustrates such a circuit incorporating the improved Waveshapingfeature of the present invention. The blue horizontal convergencecircuit 42 includes the amplitudecontrolling coil 46, the sawtooth Wavecomponent circuit including the capacitor 47 and the variable resistor`d8 and the wave-shaping diode 4% previously described. These elementsfunction substantially in the salme manner as described With referenceto FIGURE 3. rlhe voltage pulses derived from the secondary Winding 38of the horizontal deflection output transformer 37 in this case, areimpressed upon vthe convergence circuit lby a blocking capacitor el.rlhis circuit also includes a series arrangement of a diode 62 and aresistor 63 connected in parallel with the convergence electrornagnetWinding 34B. The diode 623 and its associated resistor o3 serve tosuitab y proportion the A.C. and DC. components of the substantiallyparabolic current Wave impressed upon the electromagnet Winding asdisclosed in the Schopp patent. As disclosed in this patent, theproportioning is such that, at the troughs of the resultant parabolicWave, the current through the electromagnet winding has the samemagnitude irrespective of the particular shape and peak-to-pealamplitude of the Wave. This makes it easier to adjust the circuitry toeffect beam convergence over the entire luminescent screen of thekinescope. The blocking capacitor 6l prevents the direct cur-rentflowing through the diode 62 `and the resistor 63 from undesirablytraversing the secondary Winding 38 ofthe horizontal output transformer37 (EEGURE 3). Hence, the moditication of the present invention shown inFIGURE 5 achieves the same results as in the Schopp patent and inaddition etiects the improved shaping of the substantially paraboliccurrent wave as described previously with reference to ElGURES 3 and 4.

FIGURE 6 illustrates a blue horizontal convergence circuit 42; whichincludes both the .improved Wave-shaping feature and an additionalfeature of the invention which enables the convergence circuit tooperate in a manner to properly proportion the A.C. and DC. components`of the substantially parabolic current Wave traversing theelectromagnet winding at a considerably higher efficiency thanheretofore. As in the'forrn of the invention shown in and described withreference to FIGURE 3, the voltage pulses derived from the horizontaldeflection `circuit are impressed directly upon the convergence circuitwithout the use of a blocking capacitor, such as the capacitor 61 ofFIGURE 5. This circuit includes the amplitude-controlling coil do, thesawtooth wave circuit including the capacitor 4-7' and the variableresistor d3, and the wave-shaping diode 49. All of these components areconnected and operated substantially as previously described. l

Additionally there is provided a parallel arrangement of a diode 6d anda resistor d5 connected in series between the amplitude-controlling coille and the convergence electromagnetic winding. The diode ed and theresistor function to properly proportion the AC. and DC. components ofthe substantially parabolic current wave traversing the electromagnetwinding. By virtue of the series connection of these components with theelectromagnet Winding, instead of the parallel connection of the diode62 and resistor 63 of FIGURE 5, a material saving in power is achieved.Thus, the convergence circuit 42" of FIGURE 6 operates in a more eicientmanner to achieve dynamic beam convergence in a color ltineseopeoperating Vwith a relatively Wide deflection angle.

Whatis claimed is:

1. In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line deection means fordeiiectingsaid beams in a series of vertically spaced horizontal linesduring successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster,comprising: a dynamic convergence electromagnet having an energizingwinding; l

inductive means connected with said energizing winding to cooperate withsaid winding in converting voltage pulses derived from said deilectionmeans into a substantially parabolic current Wave for traversal of saidwinding; v

means including a series arrangement of a capacit-or and a resistorconnected in parallel with said energizing winding to produce asa-wtooth current wave component Ifor traversal of said winding; and

a unilateral conducting device connected only across said resistor insuch manner as to be rendered conducting only during the latter portionsof lsaid beam trace periods to improve the shape of the substantiallyparabolic current wave traversing said energizing winding.

2. In a color television receiverV including, a multiple-V beam colorkinescope image-reproducing device, yand line deflection means fordefleoting said beams in a series of vertically spaced horizontal linesduring successive beam trace periods to form a raster,

fthe combination for converging said beams at -all pointsy `of saidraster, comprising: a plurality of dynamic convergence electromagentshaving respective energizing windings; means including a coil connectedin series with yone of said energizing windings `to-cooperate with saidone winding in convent-ing voltage pulses derived from said deiiectionmeans into a substantially parabolic lcurrent wave for traversal of saidone winding;

means including a series arrangement of a capacitor and a resistorconnected in parallel with said one energizing winding to produce asawtooth current' wave component for traversal of saidone winding; and

a unilateral conducting device connected only across said resistor insuch manner as to 4be substantially non-conducting during the initialportion of each Y of said beam trace periods and to be substantiallynon-'conducting during the initial portion of each of "said beam traceperiods and to be conducting during the latter portion ol each of saidbeam trace periods Ito improve the shape of the substantially paraboliccurrent wave traversing said one energizing winding.

3. In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line deection means for deectingVsaid beams in a series of f vertically spaced horizontal lines dur-ingsuccessive beam trace periods to tor-m a raster,V Y the combination forconverging said beams at all points `of said raster, comprising: adynamic convergence clectromagnet having an energizing winding, therebeing one such electro-magnet -for each of said beams; Y means includinga coil connected in series with one of said energizing windings tocooper-ate with said one `winding in converting voltage pulses derivedfrom :said deflection means into a substantially parabolic; current wavefor traversal of said one winding; means including a seriesarrangement-oi a capacitorl rand a resistor connected in parallel withsaid one energizing winding lto yproduce a lsawtooth currentx wavecomponent for traversal of said one winding;-

a unilateral conducting device connected only across said resistor insuch manner .as to be rendered conducting only during the latter portionof each oi said beam tra'ce periods to improve the shape of thesubstantially parabolic current wave traversing said one energizingwinding.

4. In a color television receiver including, amultiplebeam colorkinescope image-reproducing device, and line; deilection means vfordeilecting said beams in a series of vertically spaced horizontal linesduring successive beam trace periodsrto form a raster,

the combination for converging said beams at all points of said raster,comprising:

a dynamic convergence electromagnet having an energizing winding, therebeing one such electromaguet for each of said beams;

means including an amplitude-controlling coil com nected in series withat least one of said energizing i windings to cooperate with said oneWinding in converting'voltage pulses derived from said deflection meansinto a substantially `parabolic current wave :for traversal of said onewinding; means including a series arrangement of a capacitor and avariable resistor connected in parallel with said one energizing windingto produce Ia sawtooth current wave component for traversal of said onewinding, the amplitude of which is determined by said variable resistor;and a diode connected only across .said resistor in such polarity as tobe rendered conducting only during :the latter portion of each of saidbeam trace periods Ito improve the -shape of the substantially paraboliccurrent wave traversing said one energizing winding. 5. In acolor imagedisplay system including, a multiplebea'm color' image-reproducingdevice, and line deflection means for deflecting said beams in a `seriesof vertically spaced horizontal lines during succe'ss've beam traceperiods to form a raster, Y

lthe combination for converging said beams at all points of said raster,comprising: a dynamic convergence electromagnet having an energizingwinding; means including a coil corrected in series with said energizingwinding to cooperate with said winding in converting voltage pulsesderived from said dflection means into a substantially parabolic currentWave for traversal of said winding; means including a rst resistorconnected in parallel with said energizing winding to produce a sawtoothY current wave component for traversal of said winding; Y

-a series arrangement of a diode and a second resistor connected inparallel with said electromagnet wind- 'ing to proportion the directcurrent and alternating :current components of thesubstantially.parabolic cur-rent was so that, at the troughs of saidwave, the current through said winding always has the same magnitudeirrespective of the particular shape and peakto-peak amplitude of saidwave; and

a unilateral conducting device connected across said first resistor insuch manner as tobe rendered conduct-ing only during the latter Iportionof each of said Ibeam trace periods to improve the shape of thesubstantially parabolic current Wave traversing said energizing winding.

6. In acolor television receiver including, `a multiple- Y Ibeam colorlcinescope imagedreproducing device, and line deflection means fordeecting sa'd beams in a series of vertically spaced horizontal linesduring successive .beam trace periods to for-m a raster,

the combination for converging said beams at all points of said raster,comprising: a dynamic convergence Velectr-omagnet having an energizingWinding; Y means including a Yseries arrangement of a capacitor i and `acoil connected in series with said energizing winding to cooperate withsaid winding in converting voltage pulses derived from said deectionmeans 'anemie into a substantially parabolic current wave for traversalof said winding;

means including a series arrangement of a capacitor and a rst resistorconnected in parallel with said energizing winding to produce a sawtoothcurrent Wave component for traversal of said winding;

a series arrangement of a diode and a second resistor connected inparallel with said electromagnet winding to proportion the directcurrent and alternating current components of the substantiallyparabolic current wave so that, at the troughs of said wave, the current`through said winding always has the isame m-agnitude irrespective ofthe particular shape yand peak-to-peak amplitude of said wave; and

a kunilateral conducting devi-ce connected across said first resistor insuch manner as to be substantially non-conducting during the initialportion of each of said trace periods and to be rendered conductingduring the latter portion of each of said beam trace periods to improvethe shape of the substantially parabolic cur-rent wave traversing saidenergizing Winding.

7. In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line deflection means fordeiiecting said beams in a series of vertically spaced horizontal linesduring successive beam trace periods to form a raster, Y

the combination for converging said beams at yall points of said raster,comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a series arrangement of a capacitor rand a variableinductance coil connected in series with said energizing winding tocooperate with said winding in converting voltage pulses derived fromsaid deflection means into a substantially parabolic -cunrent wave fortraversal of said winding, said coil serving to control the amplitude ofsaid parabolic wave;

means including a series arrangement of a capacitor and a variableresistor connected in parallel with said energizing winding to produce asawtooth current wave component for traversal of said winding, saidresistor serving to control the amplitude of 'said sawtooth wavecomponent;

a eries arrangement of a diode and a resistor connected in parallel`with said electromagnet Iwinding to proportion the direct current andalternating currentk components `of the substantially parabolic currentwave so that, at the troughs of said wave, the current through saidwinding always has the same magnitude irrespective of the particularshape and peakto-peak amplitude of said wave; and

a diode connected across said variable resistor in such polarity as to`be rendered conducting only during fthe latter portion of each of saidbeam trace periods to improve the shape of the substantially paraboliccurrent wave traversing said energizing windin".

3. in a color image display system including, a multiple-beam colorimage-reproducing device, and line deiiection means for dellecting saidbeams in a series of vertically spaced horizontal lines duringsuccessive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster,comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a coil connected in series with said energizing windingto cooperate with said winding in converting voltage pulses derived fromsaid deiiection means into a substantially parabolic current wave fortraversal of said winding;

means including a first resistor connected in parallel with saidenergizing winding to produce a sawtooth current Wave component fortraversal of said Windins;

a first unilateral conducting device connected across said firstresistor in such manner as to be rendered conducting only during thelatter portion of each of said beam trace periods to improve the shapeof the substantially parabolic current wave traversing said energizingwinding; and

a parallel arrangement of `a second unilateral conducting device and asecond resistor connected in series with said electromagnet winding toproportion the direct current and alternating current components of thesubstantially parabolic current wave so that, at the troughs of saidwave, the current through said Winding always has the same magnitudeirrespective of the particular shape and peak-to-peak amplitude of saidWave, whereby to etect convergence of said beams with a high degree ofefficiency over relatively large angles of beam deilection.

9. In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line deilection means fordetiecting said beams in a series of vertically spaced horizontal linesduring successive beam trace periods to form a raster,

the combination for converging said of said raster, comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a coil connected in series with said energizing windingto cooperate with said winding in converting voltage pulses derived fromsaid deiection means into a substantially parabolic current wave fortraversal of said winding;

means including a series arrangment of a capacitor and a first resistorconnected in parallel with said energizing Winding to produce a sawtoothcurrent wave component for traversal of said winding;

a unilateral conducting device connected across said resistor in suchmanner as to be rendered conducting only during the latter portion ofeach of said beam trace periods to improve the shape of thesubstantially parabolic current wave traversing said energizing winding;and

a parallel arrangement of a diode and a second resistor connected inseries with said electromagnet winding to proportion the direct currentand alternating current components of the substantially paraboliccurrent wave so that, at the troughs of said wave, the current throughsaid winding always has the same magnitude irrespective of theparticular shape and peak-to-peak amplitude of said wave, whereby toeffect convergence of said beams with a high degree of eciency overrelatively large angles of beam deiiection.

It). In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line deilection means fordeilecting said beams in a series of beams at all points verticallyspaced horizontal lines during successive beam trace periods to form araster,

the combination for converging said beams at all points of said raster,comprising:

a dynamic convergence electromagnet having an energizing winding;

means including a variable inductance coil connected in series with saidenergizing winding to cooperate with said winding in converting voltagepulses derived from said deection means into al substantially paraboliccurrent wave for traversal or" said winding, said coil serving tocontrol the amplitude of said parabolic wave;

means including a series arrangement of a capacitor and a variableresistor connected in parallel with said energizing winding to produce asav/tooth current wave component for traversal of said winding, saidresistor serving to control the amplitude of said sawtooth wavecomponent; a diode connected across said variable resistor in suchpolarity as to be rendered conducting only during the l latter portionof each of said beam trace periods t improve the shape of thesubstantially parabolic current Wave traversing said energizing winding;and

a parallel arrangement of a diode and another resistor connected in.series with said electromagnet winding to proportion the direct currentand alternating current components of the substantially p-araboliccurrent Wave so that, at the troughs of said wave, the current throughsaid winding always has the same magnitude irrespective of theparticular shape and peak-to-peak amplitude of said wave, whereby toeffeet convergence of said beam with a high degree of eilciency overrelatively large angles of beam deection.

11. In a color image display system including, a multiple-beam colorimage-reproducing device, and line delection means for deilecting saidbeams in a series of vertically spaced horizontal lines duringsuccessive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster,comprising:

a dynamic convergence electromagnet having an energizing winding;

means connected with said energizing winding to coopcrate with saidwinding in converting voltage pulses derived from said deflection meansinto a substantially parabolic current wave for traversal of saidwinding; and

'a parallel arrangment of a unilateral conducting device and resistivemeans connected in series with said electromagnet winding to proportionthe direct current and alternating current components of thesubstantially parabolic current wave so that, at the troughs of saidwave, the current through said winding always has the same magnitudeirrespective of the particular shape and peakto-peak amplitude of saidwaves, whereby to eiect convergence of said beams with a high degree ofeiliciency.

12. In a color television receiver including, a multiplebeam colorkinescope image-reproducing device, and line dellection means fordefiecting said beams in a series of vertically spaced horizontal linesduring successive beam trace periods to form a raster,

the combination for converging said beams at all points of said raster,comprising: a dynamic convergence electromagnet having an energizingwinding;

l2 inductive means connected in series with said energizing winding tocooperate with said winding in converting voltage pulses derived fromsaid deiiection means into a substantially parabolic current wave fortraversal of said winding; and

a parallel arrangement of a unilateral conductive device and a resistorconnected in series with said electromagnet winding to proportion thedirect current and alternating current components of the substantiallyparabolic current Wave so that, at the troughs of said wave, the currentthrough said Winding always has the same magnitude irrespective of theparticular shape and peak-to-peak amplitude of said wave, whereby toeifect convergence of said beams with a high degree of efficiency. 13.In a color television receiver including, a multiplebeam color kinescopeimage-reproducing device, and line dellection means for deflecting saidbeams in a series of vertically spaced horizontal lines duringsuccessive beam trace periods to form a raster,

the combination for converging said beams at allv points of said raster,comprising: Y

a dynamic convergence electromagnet having an energizing Winding; Y

means including a coil connected in series with said energizing windingto cooperate with said winding in converting voltage pulses derived fromsaid deilection means into a substantially parabolic current .wave fortraversal of said winding; and

a parallel arrangement of a diode and a resistor connected in seriesbetween said coil and said electromagnet winding to proportion thedirectcurrent and alternating current components of the substantiallyparabolic current Wave so that, at the troughs of said wave, the currentthrough said winding always has the same magnitude irrespective of theparticular shape and peak-to-peak amplitude of A said wave, whereby toveffect convergence of said beams with a high degree of efliciency.

References Cited by the Examiner RCA Color Television Service Data,1960, No. T5, p. 33, lune 17,1960.

DAVID G. REDI-NBAUGH, Primary Examiner.

ROBERT SEGAL, Examiner. Y

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No.,3,187,218 A' June l, 1965 Ralph R. E'del It is heteby certified thaterror appears in the above numbered patent reqiring correction and thatthe said Letters Patent should read as co;reeted,below.

Column 3, line 20, for "RSA" read RCA column 7, lines 47 to 49, strikeout "and to be substantially non-Conducting during the initial portionof each of said beam trace periods" column 8, line 52, fot "was" readwave Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER AI testing Officer Commissioner ofPatents

1. IN A COLOR TELEVISION RECEIVER INCLUDING, A MULTIPLEBEAM COLORKINESCOPE IMAGE-REPRODUCING DEVICE, AND LINE DEFLECTION MEANS FORDEFLECTING SAID BEAMS IN A SERIES OF VERTICALLY SPACED HORIZONTAL LINESDURING SUCCESSIVE BEAM TRACE PERIODS TO FORM A RASTER, THE COMBINATIONFOR CONVERGING SAID BEAMS AT ALL POINTS OF SAID RASTER, COMPRISING: ADYNAMIC CONVERGENCE ELECTROMAGNET HAVING AN ENERGIZING WINDING;INDUCTIVE MEANS CONNECTED WITH SAID ENGAGING WINDING TO COOPERATE WITHSAID WINDING IN CONVERGING VOLTAGE PULSES DERIVED FROM SAID DEFLECTIONMEANS INTO A SUBSTANTIALLY PARABOLIC CURRENT WAVE FOR TRAVERSAL OF SAIDWINDING; MEANS INCLUDING A SERIES ARRANGEMENT OF A CAPACITOR AND ARESISTOR CONNECTED IN PARALLEL WITH SAID ENERGIZING WINDING TO PRODUCE ASAWTOOTH CURRENT WAVE COMPONENT FOR TRAVERSAL OF SAID WINDING; AND